In the field of storage systems using hard magnetic disks, also known as Winchester drives, the density storage of data on the disks has reached a relatively high level. Thus, for example, in 51/4 inch disk diameter drive, each disk may have somewhat more than 1,000 tracks, and each track contains more than 20,000 bytes of information, with each byte including eight binary digits or bits of information. Thus, each side of a 51/4 inch hard disk is capable of carrying in the order of 1,000,000 bits of information, and the density of storage of information will no doubt increase, as it has in the past.
With this very high density of data storage, even slight stresses or misalignment, accentuated by vibration and/or thermal cycling, may introduce significant errors into the recording or reading of information. It is therefore most important that the mechanical arrangements for mounting the motor and the disks, as well as the magnetic head positioner, be free of undesired mechanical stresses. In addition, it is important that the mechanical arrangements be such that undue vibration or oscillations do not occur.
Two basic areas in a Winchester disk drive where stresses might otherwise be introduced, are the shafts for mounting the main drive motor and for mounting the head positioner. These two shafts are normally mounted both to a base plate and to the mounting plate forming a portion of the housing at the other end of the shaft. In some Winchester disk drive designs, these shafts have initially been secured to the base plate, and then, following enclosing the drive in the housing, the other ends of the shafts have been rigidly secured to a previously machined location on the mounting plate, forming part of the housing at the other end of the shaft. However, because of the normal slight misalignment between the two portions of the housing, relative to the two ends of the shafts, significant stresses may be established in the shafts, which eventually may be expected to produce data errors in recording and/or reading, in the course of the life of the unit, and the vibration and thermal cycling to which the units are subjected.
It is understood that it has previously been proposed to place a simple washer between the end of the shaft, and the upper mounting plate, with the washer being secured to the mounting plate by epoxy, and with a screw extending through the mounting plate and the washer into the end of the shaft. However, while this arrangement compensated for certain types of variations in shaft length or the like, the configuration did not preclude stresses and strains of other types.
Accordingly, a principal object of the present invention is to provide arrangements for mounting the end of a shaft in a Wichester drive so that it is entirely stress-free.